The classic red velvet cupcake contains just a hint of unsweetened cocoa powder, as well as buttermilk, white vinegar and vanilla extract. Once you have those in the batter, the cupcakes can be tinted any color – including the classic red, which is where the cupcakes get their name. However, you can also combine blue and violet gel food coloring to get these unabashedly patriotic blue velvet cupcakes. Once they have been coated in white vanilla buttercream frosting and some colorful sprinkles, they are ready to be enjoyed!
Source Traceys Cullinary Adventures

These are blue velvet cupcakes without the blue food coloring in the base itself. These are healthy and low in fat – exactly the recipe you’re looking for: an afternoon sweetness without the guilt. The chocolate base has a puree of blueberries but that doesn’t exactly turn the cupcakes blue. It’s when you bite on it that you start thinking about blue velvet. These are iced with a blue vegan frosting that anybody – vegan or not – will enjoy.
Source Chocolate-Covered Katie